1. Field of the Invention
The present invention relates to a musical tone signal synthesizer of the modulation type, and more particularly to a musical tone signal synthesizer wherein a sideband wave caused by modulation is utilized to synthesize a musical tone signal of a fixed formant characteristic.
2. Description of the Prior Art
Disclosed in Japanese Patent Laid-open Publication No. 2(1990)-254497 is a musical tone signal synthesizer wherein a windowing function waveform signal is repeatedly produced at a cycle corresponding with a frequency of a musical tone signal to be generated or a frequency of integer times the frequency of the musical tone signal so that a waveform signal starting from a predetermined phase at each cycle of the windowing function waveform signal is repeatedly produced at a shorter cycle than that of the windowing function waveform signal, and wherein the produced waveform signals are multiplied to synthesize a musical tone signal of a fixed formant characteristic. Disclosed also in Japanese Patent Publication No. 64(1989)-4199 is a musical tone signal synthesizer of the frequency modulation type wherein a waveform signal is produced as a carrier at a frequency of a musical tone signal to be generated or a frequency of integer times the frequency of the musical tone signal, and wherein another waveform signal is produced as a modulation wave at a frequency related to integer times the frequency of the carrier so that frequency modulation of the carrier is effected by the modulation wave to obtain a plurality of sideband waves for synthesis of a musical tone signal.
In the case that the former musical tone signal synthesizer is adapted to synthesize a musical tone signal with a plurality of formants, it is required to provide a plurality of musical tone signal synthesizers in parallel in accordance with the number of formants. This means that the whole construction of the musical tone signal synthesizers becomes complicated. In the latter musical tone signal synthesizer, a distributed condition of the sideband waves obtained by the frequency modulation may not be estimated in a simple manner. It is, therefore, difficult to synthesize a musical tone signal of a desired formant characteristic.